A proposed optical element includes regularly arranged metal structures each having a size smaller than a wavelength of an incident light enter in the optical element (the wavelength is hereinafter referred to as “an incident wavelength”) so as to control a phase and a polarization state of the incident light. For example, PLT 1 discloses an optical element that includes regularly arranged metal structures each having a size smaller than an incident wavelength and each having a V shape formed by combining two metal line portions. When an incident wave as a plane wave enters perpendicularly this optical element, the optical element generates, at a certain rate, an extraordinary light that is a polarized light component polarized in a direction different from that of the incident wave. PLT 1 describes that a wavefront of the generated extraordinary light can be controlled by controlling a phase delay amount (that is, by performing a phase control).
Some polarized light component of the incident light entering the optical element disclosed in PLT 1 is transmitted therethrough without being affected by the phase control. In contrast, the extraordinary light generated due to an effect of the metal structures can be changed in its propagating direction and can be condensed, by the phase control. In this manner, the optical element disclosed in PLT 1 provides, by the phase control, the incident light passing through the optical element with different effects depending on a polarization direction. In addition, PLT 1 discloses that an arbitrary phase distribution can be obtained by adjustment of shapes and arrangement of the metal structures.